In recent years, in acoustic apparatuses such as an audio device, audio reproduction and outputting using a surround function are generally performed. The surround function is a function of creating a stereoscopic sound field by what is called a multichannel to implement sound with realistic sensation. As such surround function system, there are various surround modes; 5.1-ch surround systems using an audio compression format such as AC-3 (trademark), DTS (trademark) or AAC (trademark), 5.1-ch surround systems such as Dolby Pro Logic (trademark), and 6.1-ch surround system such as NEO:6 (trademark) are presently in widespread use. In order to handle such surround function having a different mode, there has been devised an audio reproduction system capable of performing reproduction mode switching for each audio format (for example, Japanese Patent No. 3491417, pp. 4-5, FIG. 1).
Also, with recent advancement of digital HiVision in TV broadcast, not only audio software reproduction apparatuses such as CD (Compact Disc) or DVD (Digital Versatile Disc) but also TV receivers or the like often have mounted therein the surround function. As TV broadcast, there are two main types of broadcast modes; two-channel and multi-channel. When the original broadcast is multi-channel, it can be directly reproduced by the surround mode. However, in reproducing two-channel broadcast sound by the surround mode, a multi-channel processing (matrix processing) for creating multi-channel from two-channel must be applied to the audio signal.
The above described matrix processing is effective when the number of channels of input audio signal is smaller than the desired number of channels of audio output, but unnecessary when the number of channels of input audio signal is equal or smaller than the desired number of channels of audio output. Accordingly, in such case, the above matrix processing is prohibited. Thus, when the matrix processing is applied to digital broadcast sound, before applying the processing, a selection of whether or not to apply the matrix processing must be made according to whether the audio signal is two-channel or multi-channel. On the contrary, there is a case where it is desired to apply a down-mix processing to multi-channel audio signal to obtain a two-channel audio signal. In this case, also, before applying the processing, a selection of whether or not to apply the down-mix processing must be made according to whether the audio signal is two-channel or multi-channel.
This setting of surround mode is usually performed by the user itself watching the TV broadcast; when the user continues to watch programs having the same number of audio channels, the operation does not create so much burden for the user. However, for example, when the user alternately selects two-channel broadcast and multi-channel broadcast to watch the broadcast, the surround mode setting constitutes a significantly complicated operation. More specifically, in a case where the user watches a two-channel program and then, once selects a multi-channel program and thereafter, begins to watch a two-channel program again, the matrix processing is reset when the multi-channel is selected. Consequently, when a two-channel is selected again, the setting of surround mode has been reset, so the user watches the two-channel program as it is.
As a result, whenever the user performs switching between a plurality of channels, surround mode (reproduction mode) setting must be repeated, constituting a significantly burdensome operation. Needless to say, as for the above described down-mix processing, the same problem arises.
Also, when the audio signal is a compressed audio signal, it is occasionally desired to perform surround mode (reproduction mode) setting with respect to each of the different audio compression (AC-3 (trademark), DTS (trademark) and the like) formats In this case, also, similarly to the above described case, the user must repeat the setting according to an audio compression format of input audio signal, this constituting a significantly burdensome operation.
To address the above circumstances, the present invention has been achieved, and an object thereof is to implement an acoustic device capable of properly setting a reproduction mode.